South America

Person-to-person transmission

Andes virus is the one hantavirus with documented person-to-person transmission, first described in Argentina in the 1990s. Spread remains rare overall, but the documented household and healthcare-worker clusters have led to specific contact-tracing protocols in confirmed Andes-virus events. U.S. hantaviruses (Sin Nombre, New York, Black Creek Canal, Bayou) have not shown person-to-person transmission.

Geographic spread

Reported Andes-virus activity is concentrated in two countries.

• Argentina — Patagonia and adjacent rural regions; first identification in the 1990s.
• Chile — southern provinces overlapping with the long-tailed pygmy rice rat range.
• Other Southern Cone countries — sporadic confirmed cases linked to similar reservoir habitat.
• Travel-associated cases — recorded outside South America when itineraries pass through endemic range.

Why this is tracked separately from U.S. HPS

U.S. HPS surveillance describes Sin Nombre and related viruses transmitted by aerosolized rodent excreta in deer-mouse and other native rodent populations. Andes virus has a different reservoir, a different geographic distribution, and the unique person-to-person feature. Pooling Andes-virus records into U.S. HPS totals would misrepresent both the U.S. transmission profile and the size of the South American signal.

What watchers track in an Andes-virus event

Public-health communicators focus on a small set of variables when describing an Andes-virus cluster.

• Exposure window relative to itinerary, lodging, and rural-area activity.
• Reservoir overlap with the long-tailed pygmy rice rat range.
• Household and healthcare-worker contact precautions when person-to-person spread is plausible.
• Repatriation testing for returning travelers with compatible symptoms.

Current event: MV Hondius cluster (2026)

The MV Hondius hantavirus cluster is the current WHO-tracked Andes-virus event, linked to a multi-country South American cruise itinerary. Eleven records are linked to the cluster across three WHO Disease Outbreak News updates — eight laboratory-confirmed, two probable, and one inconclusive U.S. repatriated traveler. The cluster is the clearest current example of why HantaScan tracks Andes-virus records separately from U.S. HPS data.